1. Field of the Invention
The present invention relates to hybrid nanomaterial electrodes, and more particularly to hybrid nanomaterial electrodes used in a gas detector for detecting volatile organic compounds.
2. The Prior Arts
Volatile solvents and oils are frequently used in industrial applications. The evaporation of the industrial solvent can form volatile organic compounds (VOCs) dangerous to the health that is propagated in the air. Common examples of volatile organic compounds include not completely burnt oxide carbon, hydrocarbons, alkene, benzene, alcohol, aldehyde, ketons, organic compounds including nitride, alkyl halides, etc.
Volatile organic compounds are dangerous to the health. Short and temporary exposure to volatile organic compounds can cause dizziness, nausea, eye tearing, nose irritation, coughing, and even death if the concentration is excessively high. Prolonged exposure can cause lever, lung and respiratory diseases or cancers. Moreover, because they usually include hydrocarbon elements, have a low evaporation point and are easily burnt, high concentrations of volatile organic compounds may induce explosion and incendiary risks. Therefore, the detection and control of the presence of volatile organic compounds is needed to reduce these risks.
A conventional gas analyzer instrument, such as a gas chromatography instrument or mass spectrometer, can have high sensitivity and provide accurate results and a low concentration detection limit. However, it is usually large in size and not conveniently portable, relatively expensive, and the need of sampling. Therefore, the conventional gas analyzer instruction is not adapted for frequently repeated and instantaneous uses.
One type of gas detectors may typically use semiconductor materials that can have variable resistance. The semiconductor detector has a high sensitivity, is simple in structure, small in size and cost-effective to fabricate. An example of material used the semiconductor detector is titanium dioxide. The gas detector using dioxide titanium as detecting material advantageously has a high sensitivity, is cost-effective to fabricate, fast response time, and short recovery time. However, this type of gas detector usually operates at a high temperature above 300° C., which limits its application. Moreover, the installation of the titanium dioxide nanostructure (nanowires, nanotubes, nanoposts or nanostrips) on the detecting electrode requires highly accurate processing, because the quality of the assembled titanium dioxide nanostructure determines the performance of the gas detector.
Dielectrophoresis is a process in which a non-uniform electric field is externally applied to control particles owing to interaction between the electric field and the dielectric property of the particles. This process can be applied for accurately assembling nanostructures, and can be implemented in room temperature to assemble a titanium dioxide nanostructure. Test experiments have shown that dielectrophoresis can be employed to accurately assemble a single nanowire on the electrode. However, if the titanium dioxide nanowire were to be assembled in a gap between two electrodes, the inventors of the present application have discovered that the nanowire can be installed with higher accuracy when the gap between the two electrodes is smaller. But the reduction of the inter-electrode gap renders the fabrication of the electrodes more difficult and requires an electron beam lithography and etching processes, which is complex, time consuming and costly.